Gaseous electric discharge arc lamp



Oct. 31, 1939.

W. ELENBAAS 'GASEOUS ELECTRIC DISCHARGE ARC LAMP I Filed April 12, 1937 INVENTOR Will m Elenbaas i, (5%

ATTORNEY Patented Oct. 31, 1939 UNITED STATES PATENT OFFICE Willem Elenbaas, Eindhoven, Netherlands, assignor to General Electric Company, a corporation of New York Application April 12, 1937, Serial No. 136,447 In Germany April 24, 1936 4 Claims.

The present invention relates to gaseous electric discharge are lamps generally and more particularly the invention relates to such devices in which the arc voltage increases after the starting of the lampand reaches its full value after the lamp has been operating an appreciable time. One type of lamp having these voltage characteristics is known in the art as a high pressure metal vapor arc lamp.

Such lamps require a series resistance for the successful operation thereof and the series resistance can be in the form of an incandescent filament mounted externally of the container of the lamp. In such a circuit the voltage across the filament varies inversely with the arc voltage. Consequently, when the filament is designed to-be heated to incandescence' during the starting period of the arc discharge the filament is not heated sufiiciently during the operating period of the lamp when the arc voltage increases. On the other hand if the filament is designed to be heated to incandescence during the operating period of the lamp the filament is overloaded during the starting period when the arc voltage is low which causes said filament to burn out to terminate the useful life of the lamp unit.

The object of the present invention is'to provide a lamp unit comprising a gaseous electric discharge are lamp having an incandescent filament connected in series therewith in which the filament is heated to incandescence and not overloaded during the starting and operation of the arc lamp in the lamp unit. Another object of the invention is to provide a lamp unit comprising a gaseous electric discharge lamp device, an incandescent filament connected in series therewith in which the current load on the filament is substantially constant during both the starting and operating period of the gaseous electric discharge device. Further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

The invention attains its objects by connecting in series with said lamp device and said filament a resistance element having a high negative temperature coefiicient of electric resistance, that is,

the resistance of the element varies inversely with increases and the resistance thereof decreases. The current load on the incandescent filament is thus substantially constant both during the starting and the operation of the lamp device and the size of the incandescent filament relative to this current value is such that it emits light to complement and supplement the light emitted by said lamp device and has a long useful operating life. The regulation of the current flow through the filament is thus accomplished without the use of complicated switch mechanisms.

In the drawing accompanying and forming part of this specification a lamp unit embodying the invention is shown in a front elevational, partly sectional view.

Referring to the drawing the lamp u'nit comprises a gaseous electric discharge lamp device having a tubular quartz container I having electrode chambers 2 and 3 at the ends thereof. The inside diameter of the tubular part of the container I is 4 mm. and the outside diameterthereof is approximately 7.5 mm. Electrodes 4 and 5 are sealed into said container I and are mounted in said chambers 2 and 3, respectively. The distance between said electrodes 4 and 5 is about 8 mm. Said electrodes 4 and 5 consist of a coiled wire of high melting'point metal, such as tungsten, supporting; as by being coated with, a body of electron emitting material, such as barium oxide, and are heated to an electron emitting, are discharge supporting temperature by the discharge incident thereat. Said container I has a starting gas, such as argon, at a pressure of about 20 mm. and a quantity of vaporizable metal, such as mercury, therein. 7

The lamp device is mounted in an envelope 6 of vitreous material which envelope has a gaseous filling therein, such as nitrogen, at a pressure of about v600 mm. An incandescent filament I is also mounted in said envelope 6 and one end of said filament I is connected to the electrode 5 by current lead 8. Said incandescent filament I is located in a plane normal to the longitudinal axis of the container I and substantially surrounds said container I at a point midway between the ends of said container I. Said filament I is supported by support wires 9 which are secured to the current lead 8 by the glass bead I0. The other end of the filament I is connected by the currentlead I I to one end of the resistance I2. Said resistance I 2 has a high negative temperature coefiicient of electric resistance. Current lead I3 is connected to the other end of said resistance I2. The electrode 4' of the lamp device is connected to the current lead I4. Said current leads I3 and I4 are fused into the stem l5 of the envelope 6. The lamp device I, the filament I and the resistance I2 are thus connected in series The resistance I2 is a rod consisting of a sintered mixture of ceramic material and silicon.

The preferred method of making the resistance I 2 consists in the steps of first reducing ferro-silicon, having a high silicon content of about 98%, to powder form, mixing this material with clay (aluminum silicate) and tragacanth, both of these last 'named materials being in powder form, adding water to the mixture and working the latter into a homogeneous mass. Small, pressed rods of this mixture are then formed and at the ends of the rods small graphite blocks are pressed, which blocks serve as the contact parts of the resistance I2. These elements are then dried and heated to the sintering temperature of the mixture in an atmosphere of reducing gas. The resistance of the rod at room temperature and at an elevated temperature is determined by the ratio of the components intermixed with each other and also by the temperature at which sintering thereof takes place. The adjustment of these factors makes possible the manufacture of elements I2 having a desired resistance value.

A resistance I6 consisting of a high-melting point material, such as tungsten, is connected in parallel with the resistance I2 and is mounted adjacent said resistance I2. When potential fis applied across the terminals of the lamp unit current flows through the resistance I6 and the heat developed thereby raises the temperature of the resistance I2. As pointed out above the resistance ofthe element I2 decreases as the temperature thereof increases and when the lamp device is at operating equilibrium the element I2 ofiers but slight resistance to the flow of current.

When the lamp device described above is at operating equilibrium the current consumption thereof is about 0.4 ampere and the voltage across the electrodes is about 110 volts. Under these conditions the vapor pressure in the container I is about 20 atmospheres. Shortly after the discharge between the electrodes 4 and 5 of the lamp device has started and before the lamp device has reached operating equilibrium the voltage across the electrodes is about 15 volts. When the lamp unit is connected across the terminals of a 220 volt current source the filament I, the resistance I2 and the resistance I6 are designed in such manner that the filament I absorbs volts and the resistance I2 absorbs only 5 volts when the lamp device is at operating equilibrium. When the element I6 has a resistance of 240 ohms the element I2, when hot, must then have a resistance of 13 ohms when the lamp device is at operating equilibrium. When it is desired to consume a current of 0.45 ampere in the lamp unit immediately after potential is applied to the lamp device, when the voltage across the electrodes 4 and 5 is approximately 15 volts. the filament I absorbs 0.45 WX105 118 VOltS The rate at which the resistance of the element I2 changes should be approximately the rate of change in the lamp device voltage. This change is controlled by the distance of the resistance I6 therefrom, when desired. For example, the resistance I6 is mounted about said resistance I2 at a desired distance. When the resistance I6 is omitted the rate at which the resistance of the element I2 changes is regulated by controlling the dissipation of heat from said resistance I2, when desired. For example, the resistance I2 reaches its final resistance value more rapidly in a highly evacuated envelope 6 than when the envelope 6 is filled with a gas.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric lamp comprising in combination an hermetically sealed envelope, a gaseous electric discharge lamp device and a series ballast means for said device mounted in said envelope, said ballast means consisting of an incandescent filament partially surrounding said lamp device and a resistance having a high negative temperature coefficient of electrical resistance connected in series with said lamp device and said filament in said envelope to maintain the temperature of said filament substantially constant during the starting and operation of said lamp device.

2. An electric lamp comprising in combination an hermetically sealed envelope, a gaseous electric discharge lamp device mounted in said envelope, an incandescent filament mounted in said envelope and partially surrounding said lamp device, a resistance having a high negative temperature coefficient of electrical resistance connected in series with said lamp device and said filament in said envelope and another resistance having a positive coefficient of electrical resistance connected permanently in parallel with and mounted adjacent to said first named resistance to maintain the temperature of said filament substantially constant during the starting and operation of said lamp device.

3. An electric lamp comprising in combination an hermetically sealed envelope, a gaseous electric discharge lamp device and a series ballast means for said device mounted in said envelope, said ballast means consisting of an incandescent filament and a resistance having a high negative temperature coefficient of electrical resistance connected in series with said lamp device and said filament in said envelope to maintain the ternperature of said filament substantially constant during the starting and operation of said lamp device.

4. An electric lamp comprising in combination an hermetically sealed envelope, a gaseous electric discharge lamp device mounted in said envelope, an incandescent filament mounted in said envelope, a resistance having a high negative temperature coeificient of electrical resistance connected in series with said lamp device and said filament in said envelope and another resistance having a positive coefficient of electrical resistance connected .permanentlyin parallel with and mounted adjacent to said first named resistance to maintain the temperature of said filament substantially constant during the starting and operation of said lamp device.

WILLEM ELENBAAS. 

